Children on a medicine for attention deficit hyperactivity disorder may be at increased risk of suicidal thoughts and behaviour, UK experts caution.

The Medicines and Healthcare Products Regulatory Agency is warning doctors to be on the look out for warning signs.

It received 11 reports of suicidal thoughts or behaviour among an estimated 15,000 users of Strattera in the UK last year - mainly children.

Experts told parents not to be alarmed, saying the drug benefited many.

Children who are doing well on this medication should continue their treatment

Dr June Raine of the MHRA

For the majority of children on Strattera (atomoxetine), the drug's benefits outweigh any risk and they should continue on the treatment, they said.

Doctors and patients, together with parents and guardians, are being advised of this risk and should be made aware of any possible signs and symptoms as a precautionary measure.

Updated warnings will be put on the drug's patient information leaflet.

The news follows recent reports of concerns about potential suicidal side effects of commonly used antidepressants among children and teenagers.

Dr June Raine of the MHRA said: "We are advising healthcare professionals that patients should be carefully monitored for signs of depression, suicidal thoughts or suicidal behaviour and referred for alternative treatment if necessary.

Suicidal thoughts

"Children who are doing well on this medication should continue their treatment.

"Those who experience any unusual symptoms, or are concerned, should speak to their doctor to discuss the best course of action."

The drug is one of many used to help control the symptoms of ADHD - inability to pay attention and impulsiveness and hyperactivity.

The risk is very small. Parents should not be alarmed

Andrea Bilbow, chief executive of the ADHD charity ADDISS

It was licensed in the UK in July 2004 and can be given to children aged six upwards.

The most commonly prescribed treatment for those with ADHD, however, remains the stimulant Ritalin (methylphenidate).

Andrea Bilbow, chief executive of the ADHD charity ADDISS, said: "The risk is very small. The benefits still likely outweigh any risk.

"Parents should not be alarmed. If a child is on Strattera and doing well, don't stop.

"If they are concerned, they should go and discuss this with their doctor. And doctors should be screening users for suicidal thoughts."

She said because of the nature of ADHD, many children with the condition were already vulnerable and at risk of suicidal thoughts and should be monitored regularly anyway.

"These kids what ever drug they are on do need to be monitored more often."

She said around 40,000 children in England and Wales had been diagnosed with ADHD and were on some form of medication for the condition.

However, because ADHD is under-recognised, as many as 400,000 could actually have the condition, or 5% of children.

The drug's manufacturer Eli Lilly said that while suicidal thinking was uncommon in patients on the medication during clinical trials, it was important for parents to be aware that it can occur and to discuss any unusual symptoms with their child's doctor.